Accurate Optical Coherence Tomography (OCT) measurements or dimensional analysis require the displayed tomographic image to correctly represent physical space (i.e. conversion from image pixels to physical mm). This requirement is complicated by factors such as varying object refractive indexes (catheter optics, sheath, lumen, tissue) and the arbitrary location (in z) of relevant image features due to mismatch in the interferometer's sample and reference paths.
Most current methods require the user to manually calibrate the image by adjusting the Z-Offset position (reference arm path length) until the outer diameter of the catheter sheath aligns with fixed tick marks on the screen. This method can be time consuming and lends itself to operator error. Additionally, once the catheter is shifted from the original calibrated position, the calibration can be thrown off due to time-varying mechanical strain (e.g. pullback motion or manipulation of PIM cable) or thermal changes (room temp vs. body temp).